Battle of Copenhagen Day is observed in Denmark every April 2, commemorating the First Battle of Copenhagen, which took place on this date in 1801. This military flag flying day honors the memory of those who fell during the naval battle between the British Royal Navy and the Dano-Norwegian Navy, sparked by British fears of a Danish alliance with France. The battle resulted in significant losses for Denmark, with between 1,600 and 1,800 casualties and the capture or destruction of several Danish ships. Despite the defeat, the anniversary was designated as a flag flying day to remember the event and its participants. Like other military flag flying days in Denmark, it is a working day, and the observance serves as a reminder of the historical conflict and its implications.